In FIG. 10, a conventional oxygen mask is shown. A conventional oxygen mask apparatus 101 shown in FIG. 10 differs from an oxygen mask apparatus 1 according to an embodiment of the present invention shown in FIGS. 1 to 8 in points to be described below. That is, in the conventional oxygen mask apparatus 101, a first connector 102 is attached to a mask main body 103 such that the axis of the first connector 102 extends in a substantially vertical direction. In addition, a second connector 104 is formed into a substantially cylindrical shape so that the axis of the second connector 104 extends in a substantially vertical direction. Therefore, oxygen gas which rises substantially vertically from a gas supply tube 105 rises substantially vertically in a third connector 106, and is introduced to the second connector 104. Also, this oxygen gas introduced to the second connector 104 rises in the first connector 102. Accordingly, the oxygen gas rises in the mask main body 103 while diffusing from a relatively large upper-end opening 107 of the first connector 102. Therefore, a mask wearer 111 can relatively easily inhale, from the nostrils, the oxygen gas having flowed to a portion, below a nose 112, and the vicinity. Reference numeral 113 denotes three left slit-like holes.
In the conventional oxygen mask apparatus 101 shown in FIG. 10, the upper-end opening 107 of the first connector 102 has substantially the same diameter as that of an inner circumferential hole (in other words, a through hole) 114 of the first connector 102. Accordingly, the oxygen gas flowing into the mask main body 103 from the upper-end opening 107 may evenly spread to a substantially whole interior of the mask main body 103. To allow the mask wearer 111 to properly inhale the oxygen gas from the nostrils, therefore, a relatively large amount of the oxygen gas must be supplied into the mask main body 103. Accordingly, especially when the mask main body 103 is not well fitted on a face 115 of the mask wearer 111, the oxygen gas having risen in the mask main body 103 may flow out from the upper end and the vicinity of the mask main body 103, and flow toward an eye 116 of the mask wearer 111. As a consequence, the eye 116 of the mask wearer 111 may become dry, and the mask wearer 111 may have discomfort on the eye 116. In addition, the three slit-like holes 113 are formed on each of the left and right sides of the conventional oxygen mask apparatus 101. When the mask wearer 111 exhales a large amount of breath, the internal pressure of the mask main body 103 rises, so the mask wearer 111 becomes uncomfortable. Also, this uncomfortable feeling becomes significant if the volume of air to be breathed in and out increases.
To correct the above-described drawback of the conventional oxygen mask apparatus 101 shown in FIG. 10, an oxygen mask apparatus 121 of a modification shown in FIG. 11 can be formed by deforming the conventional oxygen mask apparatus 101. More specifically, in this oxygen mask apparatus of the modification shown in FIG. 11, left and right large ventilation holes 122, which can substantially be the same as left and right large ventilation holes 22a and 22b shown in, e.g., FIG. 1, are formed instead of the three slit-like holes 113 in the conventional oxygen mask apparatus 101 shown in FIG. 10. In the oxygen mask apparatus 121 of the modification shown in FIG. 11, therefore, the ventilation holes 122 are larger than those of the conventional oxygen mask apparatus 101 shown in FIG. 10, so the uncomfortable feeling of the mask wearer 111 when he or she breathes can be improved. However, a large amount of oxygen gas introduced from the upper-end opening 107 of the first connector 102 to a gas introduction space 123 may flow outside the mask main body 103 from the large holes 122, or a large amount of air may flow into the gas introduction space 123 of the mask main body 103 from outside the mask main body 103 and mix with the oxygen gas. When using the oxygen mask apparatus 121 shown in FIG. 11, therefore, it is relatively difficult to allow the mask wearer 111 to inhale the oxygen gas at an appropriate concentration.